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我正在尝试将一个列表（其中 Show 是我的实现 IXmlSerializable 的类）存储到本地隔离存储中。我正在使用此页面中的代码：http: //metrostoragehelper.codeplex.com/ 我已经实现了问题部分中建议的更改。当从项目列表中单击它时，我正在使用以下代码添加一个 Show 对象。

private async void addShowButton_Click_1(object sender, RoutedEventArgs e)
    {
        var isoStorage = new StorageHelper<List<Show>>(StorageType.Local);

        List<Show> currentShows = await isoStorage.LoadASync("myShowsEx");
        if(currentShows == null) {
            currentShows = new List<Show>();
        }

        currentShows.Add(currentShow);

        isoStorage.SaveASync(currentShows, "myShowsEx");


        //Read it back, for debugging to check if it has been added properly. 
        List<Show> currentShowsRB = await isoStorage.LoadASync("myShowsEx"); //Exception here

    }

第一个节目添加得非常好，它显示在 currentShowsRB 列表中。单击第二个项目并调用上述方法时，最后一次 LoadAsync 调用发生异常：访问被拒绝。（来自 HRESULT 的异常：0x80070005 (E_ACCESSDENIED)）如何解决此问题以访问本地数据存储以进行多次调用？

下面也是来自 StorageHelper 的相关代码：

public async void SaveASync(T Obj, string FileName)
    {

        FileName = FileName + ".xml";
        try
        {
            if (Obj != null)
            {
                StorageFile file = null;
                StorageFolder folder = GetFolder(storageType);
                file = await folder.CreateFileAsync(FileName, CreationCollisionOption.ReplaceExisting);

                using (var writeStream = await file.OpenAsync(FileAccessMode.ReadWrite))
                {
                    Stream outStream = Task.Run(() => writeStream.AsStreamForWrite()).Result;
                    serializer.Serialize(outStream, Obj);
                    //writeStream.Dispose(); //Added and we get UnauthorizedAccessException
                    // outStream.Dispose(); //Added ObjectDisposedException caught in catch statement below
                }
            }
        }
        catch (Exception)
        {
            throw;
        }
    }
    public async Task<T> LoadASync(string FileName)
    {
        FileName = FileName + ".xml";
        try
        {
            StorageFile file = null;
            StorageFolder folder = GetFolder(storageType);
            file = await folder.GetFileAsync(FileName);
            using (var readStream = await file.OpenAsync(FileAccessMode.Read))
            {
                Stream inStream = Task.Run(() => readStream.AsStreamForRead()).Result;
                inStream.Position = 0;
                return (T)serializer.Deserialize(inStream);
            }
        }
        catch (FileNotFoundException)
        {
            //file not existing is perfectly valid so simply return the default 
            return default(T);
            //throw;
        }
        catch (Exception)
        {
            //Unable to load contents of file
            throw;
        }
    }

我添加了 writeStream.Dispose() 行，但即使包含此行，我也会收到相同的访问被拒绝的错误消息。如果我还包括 outStream.Dispose() 行，那么我会在下面的 catch 语句中捕获一个 ObjectDisposedException。还有什么我应该做的吗？

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2 回答 2

2

您不是在等待 SaveAsync 完成，而是在 Save 仍在进行时尝试加载。将其更改为：

//isoStorage.SaveASync(currentShows, "myShowsEx");
await isoStorage.SaveASync(currentShows, "myShowsEx");   

List<Show> currentShowsRB = await isoStorage.LoadASync("myShowsEx");

编辑，awaiting on void是一个标准问题。
快速修复是：

 await TaskEx.Run(() => isoStorage.SaveASync(currentShows, "myShowsEx"));

但你也可以在TaskEx.Run()里面移动SaveASync()。并且给定一个以 Async 结尾的名称，它不应该是void：

Task SaveASyncT Obj, string FileName)
{ 
    return TaskEx.Run() => { .... }
}

我不相信 Serialize 有异步版本，所以它保持在TaskEx.Run().

于 2012-08-12T19:56:06.667 回答
0

该块可以缩短为：

        using (var readStream = await file.OpenAsync(FileAccessMode.Read)) 
        { 
            return (T)serializer.Deserialize(readStream); 
        }

因为您可以直接从 XmlSerializer 类中的流中读取/写入。

您可能还会发现 CreationCollisionOption.ReplaceExisting 可能会导致问题，并且 OpenIfExists 将导致文件被序列化程序根据需要覆盖。

于 2012-08-29T03:54:18.493 回答